The use of multi-contact recording electrodes for measuring brain electrical activity of epileptic patients has been carried out for many years. These electrodes can be of various shapes and types. Two especially common designs are the surface or cortical design, which are flat electrodes to lay on the surface of the brain, and depth electrodes, which are slender cylindrical structures that can be implanted directly into the mass of the brain. In both of these electrodes, multiple contacts are used to record the activity at several sites in the brain simultaneously so as to try to determine the focus of the epileptic seizure in the patient's brain.
A long-standing problem with such multi-contact electrodes is a simple but reliable external connection means to external monitoring apparatus. Typically, the electrode will have a lead cable or tubing which carries several lead wires from the brain electrical contacts externally to a terminal mount. The terminal mount, in turn, will be connected via a second cable to external monitoring apparatus such as an EEG monitor. The terminal mount on the electrode should preferentially be very narrow so that it can be tunneled underneath the patient's skin from the incision site to an external exit site. This tunneling process is used typically to minimize the chance of migratory bacteria directly entering the surgical wound. Thus, it is desired that the terminal mount on the electrode be very narrow so that it can be tunneled under the skin by passing it through a hypodermic needle which has already been inserted through the skin tunnel.
A particularly useful design for the terminal mount is a configuration which utilizes a linear array of concentric terminal rings mounted on tubular sheathing. This terminal mount design has been adapted for use with several different styles of connector assemblies. For example, Putz (U.S. Pat. No. 4,850,359) describes a connector comprised of two blocks or pieces with a space or major groove between them, the space or groove being designed to accept the linear array of conductors of the electrode's terminal mount. The groove or space includes take-up terminals arranged in a linear array. The electrode terminal mount is positioned into the space or groove, and the two connector blocks or pieces are clamped or brought together to assure electrical contact between the electrode terminal mount conductor array and the array of take-up terminals located within the space between the two blocks or pieces of the connector means. Another connector assembly described by Putz (U.S. Pat. No. 4,869,255) is a connector block with an elongate cavity to hold the electrode terminal mount, and an array of intersecting perpendicular holes. The cavity and the holes are described as being a first and a second space within the connector block. An additional piece or element is taught in this Putz patent and is referred to as a conductor support. The conductor support holds an array of mating conductor pins. To make an electrical connection, the array of pins on the conductor support is inserted into the matching array of holes on the connector block. As the array of pins enters the cavity, or first space into which the terminal mount electrode array has been inserted, the pins push into contact with the terminal mount array, thereby making electrical connection with the terminal mount array. Each of the designs described above by Putz involves connector assemblies with two or more separable pieces. Since a surgeon may use up to eight or ten electrodes per patient, the likelihood of losing or dropping one of these connector pieces in the operating room, rendering it non-sterile, presents a particular problem. In addition, the complexity of assembly of these connector parts can make the assembly quite time consuming, which also is a deficit in a busy operating room. Furthermore, the designs of Putz have geometric and physical complexities. For example, the use of two blocks with a space between them and the action of moving the blocks together so as to more the take-up terminals into contact with the electrodes terminal mount array involves a complex of pieces, holding elements, and conductor arrays with potentially difficult to control forces on the conductor arrays and resulting variability of array contact and possible unwanted distortion of the terminal mount array conductors. As another example, in the Putz patent, the use of first and second spaces in the connector block with an additional conductor support element, having conductors such as pins, to be inserted into the second spaces so as to move into the first space and therein to forcibly contact and distort the conductor array of the electrode terminal mount, poses a complex geometry, criticality of tolerances of many parts, potential overstress and overdistortion of the terminal mount's conductor array, resulting variability of electrical contact, etc.
The present invention involves a different and novel approach to this multi-electrode connection problem. It provides a connector assembly design which is extremely easy to use, yet provides reliable electrical connections and unique and simple geometry and action.
Among the objects of the present invention, without limitation to its scope and novelty, include:
A simplified connector block with fewer separable elements and/or simpler geometry;
A design which does not require two block-like elements to close down on a space between them, and in turn pushes upon connector contact arrays so as to contact electrode contact arrays within said space;
A design which does not require two communicating spaces in the connector block with a connector support element or conductive elements to be moved into the second space so as to squeeze on a connector array or electrode array in the first space;
A design which has, in one embodiment, a single cavity in the connector block into which the terminal array can be inserted, and a spring-loaded connector contact array within said cavity, and having an actuator means within said cavity to hold said spring-loaded array open so that said terminal array can be inserted into said cavity without contacting said spring-loaded array, and then said actuator means can cause said spring-loaded array to close or to release upon said terminal array so as to put predictable and/or proper pressure of contact on or between said two arrays for superior reliability and durability.